The paper describes both simulated and experimental results observed i
n high cyclotron harmonic peniotron oscillators with magnetron wavegui
de resonators and discusses the operation modes of the oscillation, We
made the modes clear by considering interactions between an axis enci
rcling electron beam and the space harmonic components of the respecti
ve modes generated in the magnetron waveguides. To make it possible to
operated at higher frequencies, we introduced a new concept for desig
ning high cyclotron harmonic tubes based on a space harmonic of the 2
pi mode interaction, we then presented design parameters for a number
of peniotron tubes operable up to 300 GHz with relatively low magnetic
field.